Of uncertain origin. Possibly from the application of the sense punk (“rotten wood dust used as tinder”) (see below) to anything worthless (that sense being attested since 1869), and then to any undesirable person (since 1908). The word is alternatively sometimes suggested to derive from Spanishpu(n)to (“prostitute”); this is supported by the sense development (it originally meant "prostitute", then "bottom, catamite"), but is phonologically unstraightforward.[1]

I know what you're thinking, punk. You're thinking, "Did he fire six shots or only five?" Well, to tell you the truth, I've forgotten myself in all this excitement. But being as this is a .44 Magnum, the most powerful handgun in the world, and would blow your head clean off, you've got to ask yourself a question: Do I feel lucky? / Well, do ya, punk?

(uncountable) A social and musical movement rooted in rebelling against the established order.

(uncountable) The music of the punk movement, known for short songs with electric guitars, strong drums, and a direct, unproduced approach.

(countable, sometimes as informal plural punx) A person who belongs to that movement and/or listens to that music, a punk rocker.

The relatively tame 21st century usage of punk to mean "prank" was popularized by the American television show Punk'd. Until as recently as the late 20th century, punk still connoted rape or submitting to anal rape (punk-out). The second use of the term punk-out is now comparable to acting like a pussy and mildly implies submissive behavior in general.